The development of hydrokinetic turbines is often based on idealized flow conditions which do not fully reflect river or tidal currents. In this regard, this thesis investigates the effect of non-aligned or sheared flows on the performances and loading of two turbine types: the axial rotor (ART) and oscillating foil (OFT) turbines. This study was conducted with unsteady numerical simulations and the obtained results show that for both turbine types, misalignment produces a reduction in power and thrust, while the shear has a limited effect on those quantities. The additional loading on the support structure caused by the non-idealized flow is also similar for both devices. However, misalignment and shear affect more severely the fatigue loading on ART blades than they do for OFT.